What causes the pressure in a gas

gas pressure is caused when gas particles hit with the walls of their container the more often the particles hit with the walls and the faster they are moving when they do this the higher the pressure

Name one very important thing that separates the Plant kingdom from all other kingdoms.

Explanation:

well in order to answer this question you have to provide more information < 3

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.